Internal ilio-lumbar fixator

ABSTRACT

Indirect lumbo-sacral fixation makes use of intact powerful ligaments joining the ilium to the sacrum by providing internal ilio-lumbar fixation in which tulip type pedicle screws (30) are screwed into the pedicles (46,48) at one side of the lowest lumbar vertebrae (47, 49) and are rigidly connected to a pelvic plate (31) secured by bone screws (52) to the posterior face of the adjacent ilium (51), the connection comprising a bent rod (32) having a knurled (or splined) spinal portion (33) secured in the pedicle screws by grubscrews (37) and locking screws (38) and having a non-circular male pelvic portion (35) fitting a mating female hole (40) and secured therein by a locking screw (41). Alternatively, the connection can include a universal joint between the pelvic portion of the bent rod and the pelvic plate, with three mutually perpendicular lockable pivotal connections.

This is a 35 U.S.C. 371 application based on PCT/GB92/01957, filed Oct.26, 1992.

FIELD OF THE INVENTION

This invention relates to internal ilio-lumbar fixation. Fixing of theilium to the lower lumbar vertebrae may be required for (a) variousdiseases of the vertebral column; or (b) fractures and/or dislocationsof the sacro-iliac joint region resulting in an unstable hemi-pelvis;this fixation being necessary to indirectly immobilise the lumbo-sacralsegment whilst fusion is taking place after a bone graft, to stabilisean unstable lumbo-sacral spine due to fracture or disease, to reduce andcorrect a deformity of the spine, or to reduce and immobilise asacro-iliac region fracture or dislocation until healing has takenplace.

BACKGROUND OF THE INVENTION

In the past, ilio-lumbar fixation has been attempted by (a) the Magerlmethod in which external fixator pins are applied from behind totransfix the posterior mass of each ilium and other pins transfix thepedicles of a lumbar vertebrae, these fixators then being connected byan external frame, but this method has a very limited application andhas not been generally adopted; (b) the Galveston method in which rodsaffixed to the spine by various means are passed through or into theposterior iliac mass from medial to lateral, being used mainly for veryextensive corrections of spinal deformity when there is a need to fixthe lumbo-sacral segment, affording limited stability to this segment inthe saggital plane but only very poor stability in the coronal plane androtation.

Many methods also exist that attempt to achieve direct lumbo-sacralfixation, i.e. between the lowest lumbar vertebrae and the sacrum, allof which use some form of screw fixation into the sacrum itself, butthere is a danger of damaging nerves in or exiting from the sacrum, andthe poor mechanical quality of sacral bone makes the strength of thescrew fixation to the sacrum unpredictable.

SUMMARY OF THE INVENTION

The present invention achieves an indirect lumbo-sacral fixation makinguse of intact powerful ligaments joining the ilium to the sacrum.

According to one aspect of the present invention, for use when there isno structural disruption and the sacro-iliac ligaments are intact, aninternal ilio-lumbar fixation comprises at least one pedicle screw ofthe tulip type, a pelvic plate (preferably curved to match an iliaccrest formation), and a bent rod having a spinal portion for engagementin the bifurcated head of the pedicle screw and a pelvic portion forengagement with the pelvic plate; in which combination:

the pedicle screw has a washer within its bifurcated head to embrace thespinal portion of the bent rod and to be pressed into firm engagementtherewith by the usual grubscrew screwing into the bifurcated head, andat least one additional locking screw in a screwthreaded hole throughone side of the head to engage the spinal portion of the bent rod;

the pelvic plate has at least two holes for bone screws, another holehaving a non-circular female cross-section, and a locking screw in ascrewthreaded hole opening into at least one side of the female hole;

and the bent rod having a mating male cross-section along a major partof its pelvic portion affording a close sliding fit in the female holein the pelvic plate.

In use, the bifurcated tulip type pedicle screw is screwed into a holein one pedicle of the lowest lumbar vertebra, the spinal portion of thebent rod is fitted into the bifurcated head of the pedicle screw withthe pelvic portion projecting through a notch in the adjacent ilium andprojecting up to or beyond the posterior face of that ilium, the pelvicplate is engaged with the pelvic portion of the bent rod by fitting ofthe female hole on to the part of the bent rod having a mating malecross-section and, with the pelvic plate extending over the posteriorface of the ilium, the pelvic plate is secured to the ilium by bonescrews. The washer is fitted into the bifurcated head of the pediclescrew and pressed into firm engagement with the spinal portion of thebent rod by screwing the usual grubscrew into the bifurcated head, andthe locking screw in the pelvic plate and the additional locking screwin the pedicle screw are screwed in tight against the pelvic portion andthe spinal portion respectively of the bent rod.

The angle between the spinal portion and the pelvic portion of the bentrod can be adjusted by the surgeon, if necessary, for example to producespinal lordosis and/or to fit the pelvic portion easily into the femalehole in the pelvic plate.

The final fixation of the rod at the spinal and pelvic ends dan be donein distraction, compression lordosis, kyphosis or in situ as required byvarious indications.

The spinal portion of the bent rod may be knurled or splined and theface of the washer for engagement therewith provided with acomplementary formation.

The spinal portion of the bent rod is preferably long enough to enableit to fit within a second pedicle screw of the tulip type screwed intothe corresponding pedicle of the next vertebra.

The pelvic plate preferably has a thicker portion in which is providedthe female hole and the locking screw hole, and the female hole may beprovided at one end of the pelvic plate, or it may be providedintermediate the ends of the pelvic plate, to allow for selectivevariation in the disposition of the pelvic plate on the posterior faceof the ilium.

The female hole may have a polygonal cross-section which is preferablytwelve-sided thus providing 30° increments of adjustment in the positionof the pelvic plate in relation to the bent rod, the pelvic portion ofwhich has a corresponding polygonal cross-section. Alternatively, thepelvic portion of the bent rod may be splined e.g., with twenty splinesproviding 18° increments of adjustment, and the female hole is providedwith at least one mating rib.

When using the device for sacro-iliac region fracture dislocations it isapplied only on the side of the injury. In the surgery for spinaldiseases or injuries the device will be usually applied bilaterally.Further stability may be obtained by adding a metal bridging segment toconnect the right and left rods.

According to another aspect of the present invention, for use whenreduction of a pelvic fracture or other fracture or dislocation in thesacro-iliac area is required, an internal ilio-lumbar fixation comprisesat least one pedicle screw of the bifurcated type, a pelvic plate(preferably curved to match an iliac crest formation), a bent rod havinga spinal portion for engagement in the bifurcated head of the pediclescrew and a pelvic portion for connection to the pelvic plate, and twouniversal joint members between the spinal portion of the bent rod andthe pelvic plate, in which combination:

the pedicle screw has a washer within its bifurcated head to embrace thespinal portion of the bent rod and to be pressed into firm engagementtherewith by the usual grubscrew screwing into the bifurcated head, andat least one additional locking screw in a screwthreaded hole throughone side of the head to engage the spinal portion of the bent rod;

the pelvic plate has at least two holes for bone screws and another holefor a screw forming a first lockable pivotal connection with one of theuniversal joint members;

the pelvic portion of the bent rod has a second lockable pivotalconnection with the other universal joint member the axis of which isperpendicular to the first lockable pivotal connection;

and the universal joint members are joined together by a third lockablepivotal connection the axis of which is perpendicular to the first andsecond lockable pivotal connections respectively.

In use, the tulip pedicle screw is screwed into a hole in one pedicle ofthe lowest lumbar vertebra, the spinal portion of the bent rod is fittedinto the bifurcated head of the pedicle screw, with the pelvic portionextending anteriorly alongside the adjacent ilium, the washer is fittedinto the bifurcated head of the pedicle screw and pressed into firmengagement with the spinal portion of the bent rod by screwing the usualgrubscrew into the bifurcated head, the additional locking screw in thepedicle screw is screwed in tight against the spinal portion of the bentrod, the pelvic plate is secured to the posterior face of the ilium bybone screws with the hole for the screw forming the first lockablepivotal connection in register with a notch in the ilium, which notchenables the universal joint members to be fitted between the pelvicplate and the pelvic portion of the bent rod, and all three lockablepivotal connections are tightened up to secure the ilium (or the part ofit to which the pelvic plate is secured) in correct relative dispositionto the lumbar vertebra.

The spinal portion of the bent rod is preferably knurled or splined andthe face of the washer for engagement therewith is preferably providedwith a complementary formation.

The spinal portion of the bent rod is preferably long enough to enableit to fit within a second pedicle screw the bifurcated head type screwedinto the corresponding pedicle of the next vertebra.

The second lockable pivotal connection may be formed by the pelvicportion of the bent rod being screwthreaded and fitting through a holein its respective universal joint member, with a pair of nuts on thescrewthreaded portion to bear against opposite faces of that jointmember.

The third lockable pivotal connection may be formed by a screw extendingfrom one of the universal joint members through a hole in a lug on theother universal joint member, and a nut screwing on to the screw; andthe mutually facing faces of the one joint member and of the lug of theother joint member may be provided with radiating mating ribs andgrooves to afford positive locking of the third pivotal connection.

The hole for a screw forming the first lockable pivotal connection maybe provided at one end of the pelvic plate, or it may be providedintermediate the ends of the pelvic plate, to allow for selectivevariation in the disposition of the pelvic plate on the posterior faceof the ilium.

Preferably the pedicle screws are cannulated so that they can beintroduced over a guide wire. In practice a surgeon, in order toestablish the exact path for the introduction of the screw, will make aportal into the appropriate vertebrae, by means of an awl (or the like)and then introduce a guide wire passing through the centre of thepedicle into the body of the vertebrae. The position of the guide wireis then checked by means of an imaging technique, and once the surgeonis satisfied that said wire lies in the correct position the pediclescrew is driven over the wire. It can be seen that the provision ofcannulated pedicle screws, thus enabling the screw to be positioned bymeans of a guide wire, considerably reduces the likelihood ofinadvertently piercing the spinal canal with the screw, so avoidingcausing damage to the neural structures therewithin.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of both aspects of the invention will now be described, byway of example only, with reference to the accompanying drawings inwhich:

FIG. 1 is an elevation of a basic embodiment in accordance with thefirst aspect of the invention;

FIG. 2 is a fragmentary elevation in the direction of the arrow II inFIG. 1;

FIG. 3 is a fragmentary elevation in the direction of the arrow III inFIG. 1;

FIG. 4 is a plan view of FIG. 3;

FIG. 5 is an enlarged fragmentary view partly in section on the lineV--V in FIG. 1;

FIG. 6 is a plan view of the washer visible in FIG. 5;

FIG. 7 is an underneath view of the washer;

FIG. 8 is a side elevation of the washer perpendicular to its elevationin FIG. 5;

FIG. 9 is a greatly enlarged cross-section on the line IX--IX in FIG. 1;

FIG. 10 is an elevation of a curved pelvic plate;

FIG. 11 is a section from the line XI--XI in FIG. 10 with a female holeformation corresponding to the male section shown in FIG. 9;

FIG. 12 corresponds to FIG. 9 but shows an alternative malecross-section;

FIG. 13 corresponds to FIG. 11 but shows a single rib in the female holeto mate with the male cross-section of FIG. 12;

FIG. 14 is a fragmentary perspective view showing a preferred embodimentin accordance with the first aspect of the invention in operativeposition.

FIG. 15 is an elevation of a basic embodiment in accordance with thesecond aspect of the invention;

FIG. 16 is a plan view of the embodiment of FIG. 15;

FIG. 17 is a plan view of a first universal joint member;

FIG. 18 is an elevation from the left hand side of FIG. 17;

FIG. 19 is an elevation from the left-hand side of FIG. 18;

FIG. 20 corresponds to a part of FIG. 16 showing detail of the otheruniversal joint member;

FIG. 21 is an elevation from the left-hand side of FIG. 20;

FIG. 22 is an elevation from the left-hand side of FIG. 21;

FIG. 23 is an elevation of a bent rod usable in place of the bent rodshown in FIGS. 15 and 16;

FIG. 24 is a fragmentary perspective view showing a preferred embodimentin accordance with the second aspect of the invention in operativeposition;

FIG. 25 is an elevation of a curved pelvic plate of opposite hand to thepelvic plate included in FIG. 24, and also having more bone screw holes;and

FIG. 26 is an elevation of a pelvic plate having a sharper curvaturethan those in FIGS. 24 and 25, and also having its hole for a screwforming the first lockable pivotal connection intermediate its ends.

DESCRIPTION OF THE INVENTION

The internal ilio-lumbar fixation shown in FIG. 1 comprises a pediclescrew 30 of the tulip type, a pelvic plate 31, and a bent rod 32 havinga spinal portion 33 for engagement in the bifurcated head 34 of thepedicle screw and a pelvic portion 35 for engagement with the pelvicplate; in which combination:

the pedicle screw 30 has a washer 36 (see FIGS. 5 to 8) within itsbifurcated head 34 to embrace the spinal portion 33 of the bent rod 32and To be pressed into firm engagement therewith by the usual grubscrew37 (see also FIG. 2) screwing into the bifurcated head, and anadditional locking screw 38 in a screwthreaded hole through one side ofthe head 34 to engage the spinal portion of the bent rod;

the pelvic plate 31 has three holes 39 for bone screws (not shown, butsee FIG. 14), another hole 40 having a polygonal female cross-sectionwith twelve sides (see also FIGS. 3 and 4), and a locking screw 41 in ascrewthreaded hole opening into one side of the female hole 40;

and the bent rod 32 having a mating male cross-section (see also FIG. 9)along a major part of its pelvic portion 35 affording a close slidingfit in the female hole in the pelvic plate.

The spinal portion 33 of the bent rod 32 is knurled (but may,alternatively, be splined) and the face of the washer 36 for engagementtherewith is provided with a complementary formation 42 (seeparticularly FIG. 7).

The pelvic plate 31 has a thicker portion (or boss) 43 (see also FIGS.11 and 13) in which is provided the female hole 40 and the hole for thelocking screw 41, and the female 10 hole may be provided at one-end ofthe pelvic plate (as in FIGS. 3 and 4 or FIG. 14) or it may be providedintermediate the ends of the pelvic plate (as shown in FIG. 10).

FIG. 12 shows an alternative male cross-section for the pelvic portion35 of the bent rod 32 having twenty splines 44, and the alternativefemale hole 40 is shown in FIG. 13 with a single longitudinal rib 45 forengagement in any one of the grooves between adjacent splines 44.

Although the pelvic plate 31 in FIGS. 1, 3 and 4 is straight, it ispreferable rouse curved pelvic plates such as are shown in FIGS. 10, 11,13 and FIG. 14, with a curvature to match an iliac crest formation, suchas the formation 45 shown in FIG. 14 which will now be referred to indescribing use of an embodiment of the first aspect of the invention.

The spinal portion 33 of the bent rod is long enough to enable it tospan from one pedicle 46 of the lowest lumbar vertebra 47 to thecorresponding pedicle 48 of the next vertebra 49.

Two bifurcated tulip type pedicle screws 30 are screwed one into a holein each of the pedicles 46, 48, the spinal portion 33 of the bent rod 32is fitted into the bifurcated heads 34 with the pelvic portion 35 of thebent rod projecting through a notch 50 in the adjacent ilium 51, thepelvic plate 31 is engaged with the pelvic portion of the bent rod byfitting the female hole 40 on to the mating male part, which with thetwelve sides affords increments of angular adjustment of 30° each (or,with the twenty splines 44 affords increments of 18° each) and, with thepelvic plate extending over the posterior face of the ilium, the pelvicplate is secured to the ilium by bone screws 52.

The washers 36 are fitted into the bifurcated heads 34 of the pediclescrews 30 and pressed into firm engagement with the spinal portion 33 ofthe bent rod 32 by screwing in the grubscrews 37, and the locking screw41 in the pelvic plate 31 and the additional locking screws 38 in thepedicle screws are screwed in tight against the pelvic portion and thespinal portion respectively of the bent rod.

In addition to being able to adjust the angle between the spinal portion33 and the pelvic portion 35 of the bent rod 32, the surgeon can selecta curved pelvic plate 31 to match a particular part of the iliac crestformation 45 to one side or the other, or both sides of the notch 50 inthe ilium. Final fixation of the rod 32 at the spinal and pelvic endscan be done in distraction, compression lordosis, kyphosis or in situ asrequired for any particular indication.

The internal ilio-lumbar fixation shown in FIGS. 15 and 16 (with detailsshown in FIGS. 17 to 22) comprises a pedicle screw 30, a pelvic plate 31and a bent rod 32 somewhat similar to those in the previous embodimentsexcept for a differently shaped bend 53 in the bent rod 32 and a plaincylindrical hole 54 in the pelvic plate 31 in place of the non-circularhole 40, for a screw 55 which forms a first lockable pivotal connectionwith a first member 56 of a universal joint 57 having an axis 58;

the pelvic portion 35 of the bent rod has a second lockable pivotalconnection with a second universal joint member 59 the axis 60 of whichis perpendicular to the first lockable pivotal connection;

and the universal joint members 56, 59 are joined together by a thirdlockable pivotal connection the axis 61 of which is perpendicular to thefirst and second lockable pivotal connections respectively.

The second lockable pivotal connection is formed by the pelvic portion35 of the bent rod being screwthreaded, and fitting through a hole 62 inthe second universal joint member 59, with a pair of nuts 63 on thescrewthreaded portion to bear against opposite faces of that jointmember.

The third lockable pivotal connection is formed by a screw 64 extendingfrom the first universal joint member 56 through a hole 65 in a lug 66on the second universal joint member 59, and a nut 67 screwing on to thescrew.

In FIGS. 25 and 26, which show two preferred curved pelvic plates, thehole 54 for the screw 55 forming the first lockable pivotal connectionis provided, respectively, at one end of the pelvic plate andintermediate The ends of the pelvic plate. This allows for selectivevariation of the type and disposition of pelvic plates on the posteriorface of the ilium 51 and matching the iliac crest formation 45 as againshown in FIG. 24, in which the pelvic plate is of opposite hand to thatshown in FIG. 25 (which also has more holes).

Even the smaller bent rod 32 shown in FIG. 23 has a spinal portion 33long enough to enable it to span from one pedicle 46 of The lowestlumbar vertebra 47 to the corresponding pedicle 48 of the next vertebra49, as in the preferred embodiment of the second aspect of the inventionshown in use in FIG. 24.

Two Tulip pedicle screws 30 are screwed into respective holes in thepedicles 46, 48, the spinal portion 33 of the bent rod 32 is fitted intothe bifurcated heads 34, with the pelvic portion 35 of the bent rodextending anteriorly alongside the adjacent ilium 51, washers 36 arefitted into the bifurcated heads and pressed into firm engagement withthe spinal portion of the bent rod by screwing grubscrews 37 into Thebifurcated heads, and the additional locking screws 38 in the pediclescrews 30 are screwed in tight against the spinal portion of the bentrod.

The pelvic plate 31 is secured to the posterior face of the ilium 51 bybone screws 39 with the hole 54 for the screw 55 in register with anotch 50 in the iliac crest formation 45, which notch enables theuniversal joint members 56, 59 to be fitted between the pelvic plate 31and the pelvic portion 35 of the bent rod 32, and all three lockablepivotal connections are tightened up to secure the ilium (or the part ofit to which the pelvic plate is secured) in correct relative dispositionto the lumbar vertebra.

The pedicle screws 30 have cannulae 68 (see FIGS. 5 and 16) so that theycan be introduced over a guide wire (not shown).

I claim:
 1. An internal ilio-lumbar fixator comprising at least onepedicle screw with a bifurcated head, a pelvic plate and a bent rodhaving a spinal portion for engagement in the bifurcated head of thepedicle screw and a pelvic portion for engagement with the pelvic plate;in which combination:the pedicle screw has a washer within saidbifurcated head to embrace the spinal portion of the bent rod and to bepressed into firm engagement therewith by a grubscrew secured into thebifurcated head, and at least one additional locking screw in ascrewthreaded hole through one side of the bifurcated head to engage thespinal portion of the bent rod; the pelvic plate has at least two holesfor bone screws, another hole having a non-circular femalecross-section, and a locking screw in a screwthreaded hole opening intoat least one side of the female hole; and the bent rod having a matingmale cross-section along a major part of its pelvic portion affording aclose sliding fit in the female hole in the pelvic plate.
 2. A fixatoras in claim 1, wherein the pelvic plate has a thicker portion in whichis provided the female hole and the screwthreaded hole.
 3. A fixator asin claim 1 or claim 2, wherein the female hole is provided at an endformed on the pelvic plate.
 4. A fixator as in claim 1 or claim 2,wherein the female hole is provided intermediate two ends formed on thepelvic plate.
 5. A fixator as in claim 1 or claim 2, wherein the femalehole has a polygonal cross-section.
 6. A fixator as in claim 5, whereinthe polygonal cross-section is twelve-sided.
 7. A fixator as in claim 1,wherein the pelvic portion of the bent rod is splined, and the femalehole is provided with at least one mating rib.
 8. A fixator as in claim7, wherein there are twenty splines.
 9. A fixator as in claim 1, whereinthe pelvic plate is curved to match an iliac crest formation.
 10. Afixator as in claim 1, wherein the spinal portion of the bent rod isknurled or splined and the face of the washer for engagement therewithprovided with a complementary formation.
 11. A fixator as in claim 1,wherein the spinal portion of the bent rod is long enough to enable itto fit within a second pedicle screw of the tulip type screwed into thecorresponding pedicle of the next vertebra.
 12. A fixator as in claim 1,wherein the pedicle screws are cannulated so that they can be introducedover a guide wire.
 13. An internal ilio-lumbar fixation comprising atleast one pedicle screw with a bifurcated type, a pelvic plate, a bentrod having a spinal portion for engagement in the bifurcated head of thepedicle screw and a pelvic portion for connection to the pelvic plate,and two universal joint members between the pelvic portion of the bentrod and the pelvic plate, in which combination:the pedicle screw has awasher within said bifurcated head to embrace the spinal portion of thebent rod and to be pressed into firm engagement therewith by a grubscrewsecured into the bifurcated head, and at least one additional lockingscrew in a screwthreaded hole through one side of the bifurcated head toengage the spinal portion of the bent rod; the pelvic plate has at leasttwo holes for bone screws and another hole for a screw forming a firstlockable pivotal connection with one of the universal joint members; thepelvic portion of the bent rod has a second lockable pivotal connectionwith the other universal joint member the axis of which is perpendicularto the first lockable pivotal connection; and the universal jointmembers are joined together by a third lockable pivotal connection theaxis of which is perpendicular to the first and second lockable pivotalconnections respectively.
 14. A fixator as in claim 13, wherein thesecond lockable pivotal connection is formed by the pelvic portion ofthe bent rod being screwthreaded and fitting through a hole in itsrespective universal joint member, with a pair of nuts on thescrewthreaded portion to bear against opposite faces of the respectiveuniversal joint member.
 15. A fixator as in claim 13, wherein the thirdlockable pivotal connection is formed by a screw extending from one ofthe universal joint members through a hole in a lug on the otheruniversal joint member, and a nut screwing on to the screw.
 16. Afixator as in any one of claims 13 to 15, wherein the hole for a screwforming the first lockable pivotal connection is provided at an endformed on the pelvic plate.
 17. A fixator as in any one of claims 13 to15, wherein the hole for a screw forming the first lockable pivotalconnection is provided intermediate two ends formed on the pelvic plate.